Hackers have attacked the servers of the Climatic Research Unit at the University of East Anglia and published data which they say proves that global warming is a hoax.

The hackers stole over 1,000 emails and 3,000 documents relating to climate research over the past 10 years, and have posted excerpts online. Much of the published information will be a boon to sceptics who claim that scientists are making up data about global warming.

"The volume of material published and its piecemeal nature makes it impossible to confirm what proportion is genuine," said the university in a statement.

"We took immediate action to remove the server in question from operation, and have involved the police in what we consider to be a criminal investigation. "

The university said that the attack is most likely to have been designed to influence the UN climate conference in Copenhagen next week, and that the data released is misleading.

"The following email, which I can confirm is genuine, has caused a great deal of ill-informed comment, but has been taken completely out of context and I want to put the record straight," said professor Phil Jones, director of the Climatic Research Unit.

The email reads as follows: 'I've just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years (i.e. from 1981 onwards) and from 1961 for Keith's to hide the decline. Mike's series got the annual land and marine values while the other two got April-Sept for NH land N of 20N. The latter two are real for 1999, while the estimate for 1999 for NH combined is +0.44C wrt 61-90. The Global estimate for 1999 with data through Oct +is 0.35C cf. 0.57 for 1998.'

"The first thing to point out is that this refers to one diagram - not a scientific paper - which was used in the World Meteorological Organisation's statement on the status of the global climate in 1999 (WMO-no.913)," continued professor Jones.

"The diagram consisted of three curves showing 50-year average temperature variations for the last 1,000 years. Each curve referred to a scientific paper and a key gives their details.

"Climate records consist of actual temperature records from the mid-19th century, and proxy data (tree rings, coral, ice cores, etc) which go back much further. The green curve on the diagram included proxy data up to 1960 but only actual temperatures from 1961 onwards. This is what is being discussed in the email.

"The word 'trick' was used here colloquially as in a clever thing to do. It is ludicrous to suggest that it refers to anything untoward."

Nevertheless, climate change sceptics claim that the emails are proof that scientists are conspiring to push the theory of climate change irrespective of the facts.

"The posting of private data files from the Climatic Research Unit in England reveals the sleazy, unseemly side of a number of the leading scientific proponents of global warming alarmism, including Climatic Research Unit director Phil Jones, Michael Mann, Ben Santer and Kevin Trenberth," said Myron Ebell, director of energy and global warming policy at the Competitive Enterprise Institute, which is partially funded by energy companies.

"It is clear that some of the 'world's leading climate scientists', as they are always described, are more dedicated to promoting the alarmist political agenda than in scientific research.

"Some of the emails that I have read are blatant displays of personal pettiness, unethical conniving, and twisting the science to support their political position."